Single nucleotide polymorphisms in touch DNA

Abstract

It is widely known that DNA can be recovered from body fluids such as blood, semen, and saliva. All of which are commonly encountered at crime scenes. In fact, it is often this type of evidence that leads to the perpetrator of a crime being caught. However, it is a lesser-known fact that DNA can also be recovered from skin cells left behind on an object that a person has handled or touched. This type of DNA is known as touch DNA, and can be useful in cases involving items such as bullets or shell casings that a perpetrator may have handled before firing from a gun and leaving behind at the scene.

The issue with touch DNA is that very small amounts of it can typically be recovered. The STR typing method that is commonly used to produce a suspect profile is not sensitive enough to detect these minute amounts of DNA so that a useful profile can be produced. We aim to explore the idea of SNP genotyping in touch DNA. While SNP genotyping is not as discriminatory a method as STR typing in terms of being able to exclude or include an individual as being the source of a given DNA sample, it is a more sensitive method. SNP typing holds promise in the forensic field for being able to obtain valuable information in a case through the analysis of touch DNA left on objects at a crime scene.